River Mileages: confluence or headwaters

jamierob

Posted 07 March 2012 - 08:14 PM

jamierob

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Location:Missoula, MT

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Hi Everyone- I'm putting together a map which has a lot of rivers on it and I'm planning on printing river mileages on the map. That is, little ticks with numbers to aid floaters to know how many miles they have to camp.

So, i've been searching around to find out the best way to create these numbers, and have seen many differing implementations. Some guidebooks and maps use the headwaters of a river, say two creeks that come together to from a main-stem river as mile 0, and others show the confluence of the main river into a larger river as mile 0, and count up to the headwaters.

Hi Everyone- I'm putting together a map which has a lot of rivers on it and I'm planning on printing river mileages on the map. That is, little ticks with numbers to aid floaters to know how many miles they have to camp.

So, i've been searching around to find out the best way to create these numbers, and have seen many differing implementations. Some guidebooks and maps use the headwaters of a river, say two creeks that come together to from a main-stem river as mile 0, and others show the confluence of the main river into a larger river as mile 0, and count up to the headwaters.

Is there a cartographic standard for river mileage numbering?

Thanks!

Not sure if there is a standard or not. I always measure up from a confluence. If I am on a down-river float, I don't care about the distance to the ocean or major tributary, but rather how long to the next confluence. For example, if I am floating the Middle Fork of the Salmon, I want to know the distance to the confluence of the Salmon, versus the distance to the Columbia or the Pacific Ocean. Each major tributary would have their own unique river mileage starting at 0.

Hope that helps,kru

"Ah, to see the world with the eyes of the gods is geography--to know cities and tribes, mountains and rivers, earth and sea, this is our gift."Strabo 22AD

jamierob

Posted 08 March 2012 - 10:26 AM

jamierob

Contributor

Validated Member

19 posts

Gender:Male

Location:Missoula, MT

United States

Not sure if there is a standard or not. I always measure up from a confluence. If I am on a down-river float, I don't care about the distance to the ocean or major tributary, but rather how long to the next confluence. For example, if I am floating the Middle Fork of the Salmon, I want to know the distance to the confluence of the Salmon, versus the distance to the Columbia or the Pacific Ocean. Each major tributary would have their own unique river mileage starting at 0.

Hope that helps,kru

I agree that calculating the mileage of a river system for an entire watershed with multiple large rivers would be terribly confusing. So, for the Middle Fork of the Salmon example, many guidebooks have Mile 0 as the boundary creek put-in, which isn't a headwaters or a confluence of two smaller creeks, just the most common place that people access the river to float. The book then has the final mileage at the confluence of the Middle and the Main Salmon. Other guides I've seen would have this same section of river with the mileages reversed, Mile 0 being the confluence of the Main and the Middle and the boundary creek put-in as the upper mileage, say Mile 67.

Which raises another question, should the whole river be used to calculate a mileage, including a high, narrow alpine section, or should the numbering only include the sections deemed floatable?

Bryan Swindell

Posted 08 March 2012 - 12:50 PM

Which raises another question, should the whole river be used to calculate a mileage, including a high, narrow alpine section, or should the numbering only include the sections deemed floatable?

That's a good question. I made a map once where the client wanted unfloatable portions of the river included in the measuring of the entire river, so it could be called-out as such (ie, "Miles 7-7.5 unfloatable, portage river left"). I would leave out the high-alpine stretches, unless those are used by recreationists on foot, such as fly-fishermen. Just think carefully about the audience and you should be fine.

I always take those guidebooks with a grain a salt. They're great and I buy them before a trip cause they are great to read around a campfire, but they are not a map. It would be confusing for them to say starting from mile 67 from the Boundary Creek put-in you will encounter Velvet Falls at mile 52.3 (or whatever it is). I just wouldn't compare a map to a guidebook.

If you measure upstream from a major confluence you can always add data (mileage) if need be. What do you consider a headwater? What the USGS has defined as the river or the interfluve? Kinda grey area to me.

Great question though,
kru

"Ah, to see the world with the eyes of the gods is geography--to know cities and tribes, mountains and rivers, earth and sea, this is our gift."Strabo 22AD

I always take those guidebooks with a grain a salt. They're great and I buy them before a trip cause they are great to read around a campfire, but they are not a map. It would be confusing for them to say starting from mile 67 from the Boundary Creek put-in you will encounter Velvet Falls at mile 52.3 (or whatever it is). I just wouldn't compare a map to a guidebook.

If you measure upstream from a major confluence you can always add data (mileage) if need be. What do you consider a headwater? What the USGS has defined as the river or the interfluve? Kinda grey area to me.

Great question though,kru

Edit: Deemed floatable? How much rain, how much snowfall, what kind of a vessel, what kind of skills?

"Ah, to see the world with the eyes of the gods is geography--to know cities and tribes, mountains and rivers, earth and sea, this is our gift."Strabo 22AD